UDMGINI2

UDMGINI2 allows you to define the onset of damage initiation in a unidirectional composite.

Damage initiation can be defined at the constituent level (fiber and matrix) or at the composite level. This routine is called at every equilibrium iteration for every integration point of the unidirectional composite material for which you requested a user damage initiation routine. Here is a template for the interface to UDMGINI2. Note that this subroutine will be called until fiber failure is predicted.

SUBROUTINE UDMGINI2(HMAT, HPROP, NPROPS, PROPS, NSDV, SDV, STRAIN, STRESS, DFGRD, DELT, LE, FI, SR, IFAIL, MSTATE)
    USE HELIUS
    IMPLICIT NONE
    INTEGER(HANDLE), INTENT(IN) :: HMAT
    INTEGER(HANDLE), INTENT(IN) :: HPROP
    INTEGER, INTENT(IN) :: NPROPS
    INTEGER, INTENT(IN) :: NSDV
    INTEGER, INTENT(IN) :: IFAIL(3)
    INTEGER, INTENT(IN) :: MSTATE
    REAL(8), INTENT(IN) :: PROPS(NPROPS)
    REAL(8), INTENT(IN) :: STRAIN(6,3)
    REAL(8), INTENT(IN) :: STRESS(6,3)
    REAL(8), INTENT(IN) :: DFGRD(3,3)
    REAL(8), INTENT(IN) :: DELT
    REAL(8), INTENT(IN) :: LE
    REAL(8), INTENT(INOUT) :: FI(2)
    REAL(8), INTENT(INOUT) :: SR(2)
    REAL(8), INTENT(INOUT) :: SDV(NSDV)

    ... user coding to upate FI, SR, and SDV here ...
    
RETURN
ENDSUBROUTINE

Variables Provided for Information

HMAT

A handle to the current material. This is passed to informational routines (Informational Routines) to access information about the material.

HPROP

A handle to the current material properties. This is passed to informational routines (Informational Routines) to access information about the material properties.

NPROPS

The number of user properties specified by the *USER PROPERTIES keyword in the HIN file.

NSDV

The number of user state variables requested by *DEPVAR, NUM=<NSDV> in the HIN file.

IFAIL

The current state of failure for the composite, the matrix, and the fiber. The table below shows what each value represents.

IFAIL(1)	Composite	1 - No Failure	2 - Matrix Failure	3 - Fiber Failure
IFAIL(2)	Matrix	1 - No Failure	2 - Failure
IFAIL(3)	Fiber	1 - No Failure	2 - Failure

MSTATE

The current overall state of the material. This encompasses all forms of nonlinearity present in the current material model. This value should only be used to pass to informational routines to obtain more information about the material such as the current material properties.

PROPS

The user properties specified by the * USER PROPERTIES keyword in the HIN file.

STRAIN

The current total strain (mechanical and thermal) of the composite, matrix, and fiber. The first column (STRAIN(:,1)) contains the composite strain, and the second and third columns contain the matrix and fiber strains respectively. Strains are ordered as such: ε₁₁, ε₂₂, ε₃₃, γ_12, γ₁₃, γ₂₃. The strains are oriented in the fiber coordinate system (1 - axis parallel to the length of the fiber). The fiber direction specified in the material definition does not affect the orientation of the strains (and stresses).

STRESS

The current total stress state of the composite, matrix, and fiber. The values of this two-dimensional array are ordered in the same manner as the STRAIN array.

DFGRD

The deformation gradient. This is only useful if nonlinear geometry effects are turned on. The terms are ordered as shown below.

DELT

The temperature difference between the stress free temperature and the current temperature. This includes a viscoelastic cool-down approximation if appropriate.

LE

The characteristic element length. This number is constant throughout the analysis, regardless of any deformation to the element. For ANSYS users, this number is always = 1.

Variables Updated by the User

FI

Failure indices. The first value (FI(1)) is the failure index of the matrix and the second value is the failure index of the fiber. If either value equals or exceeds one, that constituent is determined to have initiated damage and will be degraded appropriately. If only the matrix constituent is failed this subroutine will still be called to predict damage initiation in the fiber. Once both constituents have failed, this subroutine will no longer be called.

SR

Strength Ratio. The first value (SR(1)) is the strength ratio of the matrix and the second value is the strength ratio of the fiber. The strength ratio is synonymous with the factor of safety or the margin of safety. A strength ratio less than or equal to one indicates the particular constituent has failed. A strength ratio of two indicates the factor of safety is two for the particular constituent. It is best to set this to a large number (>1) for implicit analyses. The strength ratio is used for strain rate strengthening effects in explicit finite element analyses.

SDV

The user state variable(s) requested by the *DEPVAR, NUM= keyword in the HIN file.